The present invention relates generally to the fields of alpha olefin waxes. More particularly, it concerns alpha olefin wax composition having high hardness, or oxidized alpha olefin wax compositions having low viscosity.
Hydrocarbon waxes, such as alpha olefin waxes, paraffin waxes, microcrystalline waxes, polyethylene waxes, and Fisher-Tropsch waxes, are characterized by a set of basic physical property parameters, which are used to predict or correlate performance in specific applications. The most commonly cited wax physical properties are hardness, drop melting point, and viscosity. For most wax products, these fundamental properties are governed by the molecular weight. As relatively low molecular weight waxes, alpha olefin (AO) waxes are relatively soft, but have desirable high melt flow stemming from their low molecular weight. On the other hand, extremely hard waxes, such as polyethylene waxes, have desirable high physical strength, but their viscosity is usually undesirably very high due to their extremely high molecular weights.
For many wax applications, the physical strength, or the hardness of waxes, is one of the most important performance criterions in applications such as polishing (floor, furniture and automobile), coating (textile, fruit, paper), candle formulation, investment casting, and a range of industrial composite structures. It would be desirable to improve the physical strength of alpha olefin waxes for improved performance in current applications or use in applications for which they have not yet been suitable. Further, it would be desirable if an improvement in physical strength could be achieved with minimal impact on the low melt viscosity of the alpha olefin waxes. A low melt viscosity is a highly desirable process characteristic for any hydrocarbon wax to ensure adequate flow during the processing stage in many applications. A combination of high physical strength and low viscosity has been difficult to achieve in one wax product as physical strength and viscosity both generally have a positive correlation with molecular weight.
It is well known that a range of hydrocarbon waxes can be oxidized into functional waxes by reacting oxygen or oxygen-containing gas with waxes at elevated temperatures. The oxidation changes the chemical compositions via a free-radical mechanism, which converts hydrocarbon molecules of waxes into esters, acids, and other minor components. The resulting oxidized waxes can be suitable for a range of specific applications where either high polarity or functionality is required. Many applications require a substantial oxidation of the non-polar hydrocarbon waxes. As a result, many processes have been developed for maximizing the oxidation efficiency for a high level of oxidation. These processes include use of an autoclave reactor in a batch process, or a reaction column or tubular reactor in a continuous process. The typical saponification numbers of oxidized waxes can be similar to those of natural waxes. For example, the typical saponification numbers of oxidized waxes are in the range of 50-150 mg KOH/g, and typical acid numbers are in the range of 30-50 mg KOH/g.
For some specialty applications, oxidized waxes are desirable, as described in U.S. Pat. Nos. 3,901,789; 3,994,737; 4,004,932; 4,180,408; 4,240,795; 4,426,229; 6,169,148 and 6,348,547. However, oxidation of hydrocarbon waxes generally leads to compromised physical properties, such as higher viscosity, as well as discoloration from white to undesirably off-white color.
For a number of applications where an oxidized wax can be useful, it would be desirable to have an oxidized hydrocarbon wax with both adequate hardness and relatively low viscosity.